An Organic Light Emitting Diode (OLED), first published by KODAK Co. in 1987, is a display element that utilizes the light-emitting properties of an organic light-emitting material itself to achieve the displaying effect. An OLED consists mainly of a pair of electrodes and an organic light-emitting layer, wherein the organic light-emitting layer contains a light-emitting material. When an electric current is passing between a transparent anode and a metallic cathode, an electron and a hole will combine in the light-emitting material to produce an exciton, thereby causing the light-emitting material to emit light.
Fluorenes having the following chemical structure are generally used as blue light-emitting material in an organic light-emitting diode:
(Fluorene Structure and the Numbers of Carbons on the Structure)The main reasons for this are: (1) It has been found from previous studies that the fluorescence emitting wavelength of polyfluorenes ranges from 400 to 460 nm (blue light), and the polyfluorenes exhibit good thermal and chemical stabilities, thus making them suitable to be used as the main component of an organic blue light-emitting luminophor; and (2) In either solution state or solid state, the fluorescence quantum yield of polyfluorenes is good (60-804), and when used in light-emitting elements, the polyfluorenes will provide the light-emitting elements with a better light-emitting efficiency.
However, it was found during the development that polyfluorenes tend to stack, leading to a decrease in the light-emitting efficiency of the element. Therefore, the present invention provides a chiral fluorene polymer material to address the stacking problem associated with fluorenes.